At about noon today, Bitcoin's (BTC-USD) market cap was just above $1T, or 48% of the $2.13T market cap for the entirely of the cryptocurrency universe, according to CoinGecko's database of 6,816 coins.Ether (ETH-USD) - which has been on a big run to new all-time highs as bitcoin stalls/falls - is up to a 14% share of the total market cap.It's the first time since 2018 that Bitcoin has accounted for less than 50% of total crypto market cap, and the fast action in alt-coin names like Dogecoin (DOGE-USD), Litecoin (LTC-USD), ZCash (ZEC-USD) - and plenty of others - is drawing comparisons to the late-2017 blow-off top in all cryptocurrencies.